/*************************************************************************
	> File Name: 8-solve.cpp
	> Author: yufangze
	> Mail: 2224590123@qq.com
	> Created Time: 2024-11-22 15:45:25
 ************************************************************************/

#include <iostream>
#include <set>
#include <map>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;

int dir[8][2] = {
    {-2, 1}, {-1, 2}, {1, 2}, {2, 1},
    {2, -1}, {1, -2}, {-1, -2}, {-2, -1}
};

ll dp[25];
bool check[25][25];

int main() {
    int a, b, x, y;
    cin >> a >> b >> x >> y;
    check[x][y] = 1;
    for (int k = 0; k < 8; k++) {
        int dx = x + dir[k][0];
        int dy = y + dir[k][1];
        if (dx < 0 || dx > a || dy < 0 || dy > b) continue;
        check[dx][dy] = 1;
    }
    dp[0] = 1;
    for (int i = 0; i <= a; i++) {
        for (int j = 0; j <= b; j++) {
            if (j >= 1) dp[j] += dp[j - 1];
            if (check[i][j]) dp[j] = 0;
        }
    }
    cout << dp[b] << endl;
    return 0;
}
